Incandescent lamp



Nov. 30 i926.

. 1,608,936 T. R. HARRISON INCANDESGENT LAMP Filed July 5. 1924 9/ INVENTOR fW KW Patented Nov. 30,1926,

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1,608,936 F-IcE.

OF PHILADELPHIA, PENNSYLVANIA. ASSIGILJI'OR TO 013 PHILADELPHIA, PENNSYLVANIA, ACOR- INCANDESCEN'I' LAMP.

Application filed July 5,

My present invention consists in an improved incandescent lamp, primarily devised for use in an optical pyrometer of the portable type, where it is especially desirable to minimize the lamp voltage and current consumption so as to accordingly mini mize the capacity and weight of the battery supplying the lamp current when, as is usual, this battery is carried by the observer using the pyromet'er.

The generalobject of my invention is to i minimize the current consumption and voltage required in a lamp of the character described, to obtain the desired and definite temperatures in what may be called. the optical portion of the lamp filament. In such a lamp it is essential that the temperature and brightness of the operable portion of the filament should. vary in a definite and determined-',relation' with the strength of the energizing current flowing through the filament. The temperature of the operable portion of the filament is dependent, of course, upon a heating eifect proportional to the current strength on the one hand, and on the other hand to the' rate at which the 0 'erable portion of the filament dissipates eat by radiation and by conduction into the end portions of the filament, and from the latter into the leading-in wires.

The attainment of a definite and practical maximum temperature of they operable porportions of the filament.

tion of the filament for a given strength of energizing current can be approximated by elongating the end portions of the filament proper so that practically all of the heat dissipated by the o erable portion of the filament will be radiated into space, and .only a negligible portion of the heat dissipated will be conducted away by the end This principle has heretofore been utilized in the construction of lamps of the character described, though 'it has not been found feasible in'practice to elongate the end portions of the filament sufliciently to reduce to a negligible mini-- mum the heat conduction into the end portions from the operable portion of the filament and thereby attain the desired practical maximum temperature for the latter.

In accordance with the present invention I readily secure results as good or better than those heretofore attainable in practice by means of filament end portions appreci- 1924. Serial No. 724,269.

ably shorter than have heretofore been re- 5 quired. This I accomplish by arranging each filament end portion so that there wil be a mutual or inter-radiation of heat between different sections of the portion. In consequence each end portion, or at least the section thereof adjacent the operable part of the filament, is cooled by radiation of heat into space to a lesser degree than would an equal length of filament at the same temperature, when not arranged so as to secure the inter-radiation between difi'erent sections of the end portions which is characteristic of my invention. This inter-radiation of heat between diflerent sections of each filament end portion maintains the portions at ahigher temperature than would otherwise be possible, and this more or'less counteracts the cooling effect on the operable portion caused by the conduction of heat into the filament end portions from the operable portion of the filament.

The accompanying drawing is a sectional elevation of a portion of a lamp constructed in accordance with the present invention.

The lamp shown in the drawing comprises a bulb A of conventional form, withv the usuaf leading-in wires B sealed in the base portion A of the bulb. The inner ends of the leading-in wires B are connected at the points b to the lamp filament proper. The latter comprises'an operable part 0, which in this type of lamp is ordinarily straight though it may be formed with a bend C to define the observation point for pyrometical use. Between each end of the operable part 0 of the filament, and the corresponding ament end portion C.

absorbs from the other sections of the portion a relatively large amount of radiant heat with theresultthat the temperatures of the end than would be the case but for this interheat radiation effect. The interheat radiation be- "tween different sections of a filament end portion of given length obviously depends on the relative disposition of the sections. In ordinary practice the desired effect may be readily attained by coiling the end portions into one, or more usually, two or more convolutions of small diameter. When there portions are appreciably higher are two or more turns to each end portion the heat radiation between adjacent turns decreases and increases with the distance between adjacent turns.

Having now described my invention what a I claim asnew and desire to secure by Letters Patent, is:

In an incandescent pyrometer lamp having a short operable filament portion adapted to serve as an optical-standard of compar1son, the improved means for making the temperature of said filament portion a practical maximum for a given current flo'w therethrough consisting of filament portions at the ends of said operable portion shaped Signed at Philadelphia, in the-county of Philadelphia, and State of Pennsylvania, this 30th day of June, A. D. 1924.

THOMAS RANDOLPH HARRISON. 

